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Published on: May 30, 2014
A four-state adaptive Hopf oscillator.
XiaoFu Li1, Md Raf E Ul Shougat1, Scott Kennedy1
1Department of Mechanical & Aerospace Engineering, North Carolina State University, Raleigh, NC, United States of America.
This study presents a novel analog adaptive oscillator (AO) capable of learning external stimulus frequency and amplitude. This four-state oscillator synchronizes without pre- or post-processing, advancing AO applications.
Area of Science:
- Nonlinear dynamics
- Analog circuit design
- Adaptive systems
Background:
- Adaptive oscillators (AOs) are nonlinear systems with adaptable states for information encoding.
- Previous implementations of adaptive oscillators include two-state and three-state systems using VLSI and FPGA technologies.
- Hopf oscillators are a key type of adaptive oscillator.
Purpose of the Study:
- To present an analog circuit implementation of a four-state adaptive oscillator.
- To demonstrate the oscillator's ability to learn frequency and amplitude of external stimuli.
- To verify the design through hardware measurements and simulations.
Main Methods:
- Design and fabrication of a continuous-time, analog circuit implementation of a Hopf oscillator.
- Hardware measurements and SPICE simulations for verification.
- Testing the circuit's response to complex waveforms like square waves, sawtooth waves, strain gauge data, and audio signals.
Main Results:
- The adaptive oscillator successfully learns the frequency and amplitude of external stimuli over a wide range.
- Complete synchronization is achieved without pre- or post-processing.
- Hardware measurements show good agreement with SPICE simulations.
- The circuit demonstrated functionality with diverse complex waveforms.
Conclusions:
- The developed analog adaptive oscillator offers a robust platform for learning stimulus parameters.
- This four-state adaptive oscillator advances the capabilities of previous implementations.
- Potential applications include robotic gait, clock oscillators, frequency analyzers, and energy harvesting.

